30. Thyroid Disorders Flashcards
A patient is admitted and was taking levothyroxine 100 mcg daily at home. She is NPO and provider would like the levothyroxine continued IV. What is the most appropriate dose for the pharmacist to dispense?
A. 112 mcg
B. 50 mcg
C. 200 mcg
D. 100 mg
E. 75 mcg
E. The recommended IV to PO ratio in the most recent guidelines is 0.75 to 1.
IV:PO ratio is 0.75:1, IV form not stable and should be given once prepared
Which of the following statements concerning treatment of hyperthyroidism during pregnancy is correct?
A. Methimazole is used in the first trimester of pregnancy.
B. PTU is used in the 2nd and 3rd trimesters.
C. Hyperthyroidism should not be treated during pregnancy.
D. The treatment of choice for hyperthyroidism in pregnancy is radioactive iodine.
E. Women can commonly get hyperthyroidism during the reproductive years; most cases are in females in their 30’s and 40’s.
E. PTU is used in the first trimester of pregnancy, but methimazole is used in the 2nd and 3rd trimesters due to the higher risk of liver toxicity from PTU.
Thionamides: inhibit synthesis of thyroid hormones by blocking oxidation of iodine in the thyroid gland; PTU also inhibits peripheral conversion of T4 to T3
Boxed warning: severe liver injury and liver failure (with PTU)
SE: GI upset, hepatitis, agranulocytosis (rare), pregnancy (D)
Propylthiouracil (PTU) is preferred under 2 scenarios: thyroid storm and 1st trimester of pregnancy. Otherwise use methimazole (Tapazole) in 2nd and 3rd trimester because less hepatoxicity compared to PTU
Take with food to minimize GI upset
Select the correct statements concerning levothyroxine: (Select ALL that apply.)
A. It contains T3.
B. It is the preferred agent for treating hypothyroidism.
C. It is derived from dessicated porcine gland.
D. It contains T4
E. It will lower the TSH
B, D, E. Levothyroxine is synthetic T4, not T3. The body converts T4 to T3. It is the preferred agent and matches human T4.
Tx: Levothyroxine (Synthroid, Levoxyl) is top drug
For adults <50 years of age: 1.6mcg/kg/day (IBW) – full replacement dose
Elderly, mild disease, or co-morbidities: 25-50mcg/day – partial replacement dose. We are concerned about cardiovascular problems and drug interactions
If known CVD: 12.5-25mcg/day
Boxed warning: not to be used for weight loss
SE: none, Pregnancy (A), lots of DDI (polyvalent cation, iron, orlistat, svelamer, other-separate by 4 hours; lanthanum separate by 2 hours), beta-blockers, amiodarone, steroid, PTU can decrease conversion of T4 to T3
Monitor: TSH (rarely free T4) and symptoms every 4-6 weeks until normal, then 4-6 months later, then yearly. Monitor as patient ages, may need to decrease dose; over dosing lead to Afib and fractures
IV:PO ratio is 0.75:1, IV form not stable and should be given once prepared
Take levothyroxine with water 60 minutes before breakfast or at bedtime, 3 hours after the last meal. Separate from bisphosphonates
A patient gave the pharmacist a prescription for Cytomel 25 micrograms once daily #30. Which of the following is an appropriate generic substitution for Cytomel?
A. Methimazole
B. Levothyroxine
C. Liothyronine
D. Thyroid USP
E. Propylthiouracil
C. The generic name of Cytomel is liothyronine.
methimazole (Tapazole)
levothyroxine (Synthroid, Levoxyl)
thyroid USP (Armour Thyroid, Nature-Throid)
Alison has been prescribed propylthiouracil. What common side effect might she experience?
A. Bradycardia
B. GI upset
C. Hypotension
D. Diarrhea
E. Hyperglycemia
B. Both methimazole and PTU can cause rash, and GI side effects (nausea, vomiting). With both drugs, the liver must be monitored; PTU has a boxed warning for hepatotoxicity.
Thionamides: inhibit synthesis of thyroid hormones by blocking oxidation of iodine in the thyroid gland; PTU also inhibits peripheral conversion of T4 to T3
Boxed warning: severe liver injury and liver failure (with PTU)
SE: GI upset, hepatitis, agranulocytosis (rare), pregnancy (D)
Propylthiouracil (PTU) is preferred under 2 scenarios: thyroid storm and 1st trimester of pregnancy. Otherwise use methimazole (Tapazole) in 2nd and 3rd trimester because less hepatoxicity compared to PTU
Take with food to minimize GI upset
Chief Complaint: “I have a fever and I can’t sleep”
History of Present Illness: JS is a 35 y/o male being treated for a severe MRSA skin infection. He presents to the clinic complaining of fever, nausea, increased insomnia, and “feeling like I’m going crazy”. He appears very agitated and presents with hand tremor and moist skin. He recently picked up a second job, working 60 hours a week, and attributes his worsening insomnia to stress.
Past Medical History: Insomnia (x 3 years), atrial fibrillation, MRSA skin infection diagnosed 10 days ago
Medications: Melatonin 5 mg QHS, warfarin 5mg daily, Zyvox 600 mg PO BID, MVI daily
Pertinent Social History: Alcohol 2-3x/week to help him sleep
Vitals:
Height: 5’10” Weight: 141 lbs
BP: 140/96 mmHg HR: 105 BPM RR: 22 BPM Temp: 104ºF Pain: 2/10
Labs:
Na (mEq/L) = 141 (135 - 145)
K (mEq/L) = 4.2 (3.5 - 5)
Cl (mEq/L) = 100 (95 - 103)
HCO3 (mEq/L) = 28 (24 - 30)
BUN (mg/dL) = 18 (7 - 20)
SCr (mg/dL) = 0.9 (0.6 - 1.3)
Glucose (mg/dL) = 110 (100 - 125)
Mg (mEq/L) = 1.9 (1.3 - 2.1)
PO4 (mg/dL) = 4.3 (2.3 - 4.7)
Ca (mg/dL) = 9.5 (8.5 - 10.5)
TSH (mIU/L) = 0.1 (0.3-3.0)
INR = 2.9 (2-3)
Question:
What is JS experiencing?
A. New onset hypothyroidism
B. Thyroid storm
C. Panic attack
D. Myxedema coma
E. Hypertensive crisis
B. Based on the patient’s lab values and clinical symptoms, he is experiencing thyroid storm. Thyroid storm is a life-threatening medical emergency characterized by decompensated hyperthyroidism that can be precipitated by infection, trauma, surgery, radio-active iodine treatment or non-adherence to antithyroid medication.
Thyroid Storm
Medical emergency!
S/sx: fever >103’F, tachycardia, tachypnea, profound sweating, dehydration, delirium, psychosis, coma
Tx: PTU (900-1200mg PO divided Q4-6H), iodide therapy (SSKI, Lugol’s solution Q8H), beta-blocker (to control tachycardia, palpitations, propranolol 40-80mg Q6H), steroids, aggressive cooling with APAP and cooling blankets, supportive care.
Connie uses warfarin for atrial fibrillation. Connie has just left the hospital with several new medications: levothyroxine, diltiazem and amiodarone. Select the correct statement/s: (Select ALL that apply.)
A. The levothyroxine can make the INR become supratherapeutic.
B. The diltiazem can make the levothyroxine subtherapeutic.
C. The patient will be at increased risk for forming a deep vein thrombosis.
D. The amiodarone can make the INR become supratherapeutic.
E. The diltiazem can make the warfarin subtherapeutic.
A, D. Levothyroxine can increase the INR and a patient stable on warfarin will require monitoring of the INR when levothyroxine is added. Amiodarone causes a large increase in the INR and the clinician should decrease the warfarin dose when amiodarone is added to a patient with a stable INR. Both drugs put the patient at increased risk for bleeding, not clotting.
Remember that levothyroxine increase metabolism and hence warfarin gets metabolized to active form faster leading to increased INR.
Amiodarone is a CYP inhibitor and so more warfarin.
Alison has been prescribed propylthiouracil, which should be reserved for patients who cannot use other options due to the risk of this adverse reaction:
A. Fatal skin rash
B. Liver damage
C. Trouble breathing/laryngoedema
D. Renal failure
E. Cardiotoxicity
B. PTU has a boxed warning for severe liver injury, which can come on suddenly, even after long-term use.
Chief Complaint: “I have no energy”
History of Present Illness: KB is a 32 y/o female who comes into the outpatient clinic complaining of low energy, recent weight gain of 15 pounds, foggy memory, and feeling cold even though it is sunny outside. She is diagnosed with hypothyroidism and started on levothyroxine.
Past Medical History: Allergic rhinitis, GERD, Hypothyroidism
Current Medications: Cetirizine 10 mg PRN, Mylanta 20 mL Q6H, Tylenol 325 mg Q4-6H PRN, Omega-3 fatty acid 1 gram daily, MVI daily
Vitals:
Height: 5’7” Weight: 138 lbs
BP: 129/80 mmHg HR: 85 BPM RR: 20 BPM Temp: 98.6ºF Pain: 1/10
3/10/14 Labs:
Na (mEq/L) = 141 (135 - 145)
K (mEq/L) = 4.2 (3.5 - 5)
Cl (mEq/L) = 100 (95 - 103)
HCO3 (mEq/L) = 28 (24 - 30)
BUN (mg/dL) = 18 (7 - 20)
SCr (mg/dL) = 0.9 (0.6 - 1.3)
Glucose (mg/dL) = 110 (100 - 125)
Mg (mEq/L) = 1.9 (1.3 - 2.1)
PO4 (mg/dL) = 4.4 (2.3 - 4.7)
Ca (mg/dL) = 9.5 (8.5 - 10.5)
TSH (mIU/L) = 32 (0.3-3.0)
Free T4 (mg/dL) = 0.3 (0.9-2.3)
hCG-
Plan:
Hypothyroidism. Start levothyroxine 75 mcg daily. Follow-up visit on 4/14/14.
4/14/14 Labs:
Na (mEq/L) = 143 (135 - 145)
K (mEq/L) = 4.1 (3.5 - 5)
Cl (mEq/L) = 102 (95 - 103)
HCO3 (mEq/L) = 26 (24 - 30)
BUN (mg/dL) = 15 (7 - 20)
SCr (mg/dL) = 0.8 (0.6 - 1.3)
Glucose (mg/dL) = 15 (100 - 125)
Mg (mEq/L) = 1.8 (1.3 - 2.1)
PO4 (mg/dL) = 4.1 (2.3 - 4.7)
Ca (mg/dL) = 9.7 (8.5 - 10.5)
TSH (mIU/L) = 4.7 (0.3-3.0)
hCG+
Question:
On KB’s 4/14/14 visit, what changes should be made to her drug regimen?
A. The levothyroxine dose should be increased
B. The levothyroxine dose should be decreased
C. The levothyroxine should be changed to Thyrolar
D. Thyroid replacement therapy should be discontinued
E. No changes should be made
A. KB’s serum TSH is not yet in the reference range. TSH and clinical symptoms should be checked every 4-6 weeks until they are normal. KB also has a positive pregnancy test on this visit. Pregnant women need higher levothyroxine doses throughout their pregnancies.
Can also calculate full replacement dose 1.6mg/kg/day x IBW = 1.6 x 61.59 = 98.5mcg/day
Tx: Levothyroxine (Synthroid, Levoxyl) is top drug
For adults <50 years of age: 1.6mcg/kg/day (IBW) – full replacement dose
Elderly, mild disease, or co-morbidities: 25-50mcg/day – partial replacement dose. We are concerned about cardiovascular problems and drug interactions
If known CVD: 12.5-25mcg/day
Boxed warning: not to be used for weight loss
SE: none, Pregnancy (A), lots of DDI (polyvalent cation, iron, orlistat, svelamer, other-separate by 4 hours; lanthanum separate by 2 hours), beta-blockers, amiodarone, steroid, PTU can decrease conversion of T4 to T3
Monitor: TSH (rarely free T4) and symptoms every 4-6 weeks until normal, then 4-6 months later, then yearly. Monitor as patient ages, may need to decrease dose; over dosing lead to Afib and fractures
IV:PO ratio is 0.75:1, IV form not stable and should be given once prepared
Take levothyroxine with water 60 minutes before breakfast or at bedtime, 3 hours after the last meal. Separate from bisphosphonates
Which of the following statements concerning thyroid function are correct? (Select ALL that apply.)
A. In a normally functioning system, thyroid-stimulating hormone (TSH) stimulates the secretion of thyroxine (T4) and, minimally, triiodothyronine (T3).
B. Total daily T3 production results from the peripheral conversion of T4 to T3 (roughly 80%).
C. T3 is 3-4 times as potent as T4.
D. T4 is 3-4 times as potent as T3.
E. Elevations in T4 inhibit the secretion of TSH, and a negative feedback loop is created.
A, B, C, E. T3 is much more potent than T4. T4 inhibits the secretion of TSH via negative feedback.
A patient has been prescribed Synthroid. She wishes to use a generic. Choose the correct statement/s concerning generic options for levothyroxine brand formulations: (Select ALL that apply.)
A. The correct source to check for therapeutic (AB-rated) equivalents is the red book.
B. All generics of levothyroxine are AB related to each of the available brand formulations.
C. If a patient changes manufacturers, it is prudent to monitor for symptoms of hypo or hyperthyroidism as the dosage may vary slightly.
D. Patients should be told to use brand name only.
E. Levothyroxine has a narrow therapeutic index.
C, E. The correct source to check for therapeutic (AB-rated) equivalents is the orange book. Levothyroxine comes in many dosages and various brands. One manufacturer’s dosage may not be AB-rated to the same dosage produced by a different manufacturer. If a dosage or manufacturer is changed, symptoms should be monitored. Patients should be told to try to stay with the same formulation. The pharmacist should dispense only alternatives that are AB-rated to the formulation the patient has been using.
Select the correct pathway that describes thyroid function:
A. Thyroid-stimulating hormone (TSH) stimulates the secretion of thyroxine (T4).
B. Thyroid-stimulating hormone (TSH) accounts for the majority of triiodothyronine (T3) production.
C. T3 is converted to T4.
D. Thyroid-stimulating hormone (TSH) is stimulated by elevations of T4.
E. In patients with hypothyroidism, T4 cannot be converted into T3.
A. In a normally functioning system, thyroid-stimulating hormone (TSH) stimulates the secretion of thyroxine (T4) and, minimally, triiodothyronine (T3). Total daily T3 production results from the peripheral conversion of T4 to T3 (roughly 80%).
Cheri believes she may be pregnant. She goes to see her doctor who orders various tests, including TSH and FT4. Cheri is found to have a high TSH, low FT4 and is hCG+. She is prescribed a prenatal vitamin and levothyroxine. Choose the correct statements concerning the levothyroxine pregnancy category.
A. Levothyroxine is pregnancy category A
B. Levothyroxine is pregnancy category B
C. Levothyroxine is pregnancy category C
D. Levothyroxine is pregnancy category D
E. Levothyroxine is pregnancy category X
A. When preparing for pregnancy or at the initial visit the physician will check thyroid function. If the woman is hypothyroid and it is not corrected with thyroid hormone replacement, the child will suffer neurological damage. If a person becomes pregnant while using levothyroxine, they must continue to use it and the dose will be increased. Levothyroxine is pregnancy category A.
A 40 year-old, female patient has been prescribed levothyroxine 50 mcg once daily. Choose the correct counseling statement:
A. Take this medicine with breakfast.
B. Take this medicine with lunch.
C. Take this medicine an hour before breakfast, on an empty stomach.
D. Take this medicine with dinner.
E. Take this medicine at bedtime, with a light snack.
C. Levothyroxine is taken in the morning, preferably on an empty stomach, an hour before breakfast. This optimizes the amount of drug absorbed. However, if the patient has been taking it with breakfast, do not change it. They may have had the level adjusted to the way they are using the medicine. Levothyroxine will cause insomnia if taken later in the day.
Tx: Levothyroxine (Synthroid, Levoxyl) is top drug
For adults <50 years of age: 1.6mcg/kg/day (IBW) – full replacement dose
Elderly, mild disease, or co-morbidities: 25-50mcg/day – partial replacement dose. We are concerned about cardiovascular problems and drug interactions
If known CVD: 12.5-25mcg/day
Boxed warning: not to be used for weight loss
SE: none, Pregnancy (A), lots of DDI (polyvalent cation, iron, orlistat, svelamer, other-separate by 4 hours; lanthanum separate by 2 hours), beta-blockers, amiodarone, steroid, PTU can decrease conversion of T4 to T3
Monitor: TSH (rarely free T4) and symptoms every 4-6 weeks until normal, then 4-6 months later, then yearly. Monitor as patient ages, may need to decrease dose; over dosing lead to Afib and fractures
IV:PO ratio is 0.75:1, IV form not stable and should be given once prepared
Take levothyroxine with water 60 minutes before breakfast or at bedtime, 3 hours after the last meal. Separate from bisphosphonates
What is the most common cause of hypothyroidism?
A. Lithium
B. Amiodarone
C. Hashimoto’s disease
D. Graves’ disease
E. Radiation therapy
C. The most common cause of hypothyroidism is Hashimoto’s disease, an autoimmune condition in which a patient’s antibodies attack their own thyroid gland. Drugs can also cause hypothyroidism, most notably lithium and amiodarone-both of which require monitoring of thyroid function tests.
Graves’ disease is most common cause (autoimmune) of hyperthyroidism. Remember Graves’ is hyperthyroid because it can lead to thyroid storm which is fatal and patients may end up in the “grave”. This means the Hashimoto must be hypothyroidism.
